Abstract: This study was aimed to avoid the dairy cow arthritis,which could caus huge economic losses to cattle farms.Joint effusion was collected from diseased dairy cows,and the pathogens was isolated and cultured using tryptone broth agar followed by morphological,biochemical tests and PCR amplifying 16S rRNA gene fragments and TA cloning and sequencing to identify it.It was found that the bacteria could form beta hemolytic ring on blood AGAR;And it appeared a single individual or short catenation gram-positive by optical microscopy;The results of biochemical identification showed that esculin sesquihydrate,maltose,sucrose,glucose,and hydrogen peroxide enzyme tests all presented positive;It was sensitive to cefazolin,enrofloxacin,ciprofloxacin,ampicillin,streptomycin,chloramphenicol,neomycin and cefepime,while was resistant to tetracycline,erythromycin,doxycycline and amikacin.The nucleic acid homology of this strain with Staphylococcus aureus was 91%,and with the Staphylococcus carnosus was 92%.According to the 16S rRNA gene fragment sequencing results,and the biological characteristics analysis,the initial isolates were identified as similar to Staphylococcus spp bacteria.The results of this study could provide necessary experimental basis for future diagnosis,prevention as well as treatment of arthritis in cattle farm.

Key words: dairy cow arthritis; biological characteristics; 16S rRNA; Staphylococcus spp